<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>基本选择器</title>

    <style>
        /*标签选择器，格式：标签名{}*/
        h2{
          color: blue;
        }
        /*class选择器，格式：.class名{}*/
        .article{
            color: green;
        }
        /*
        id选择器,格式：#id名{}
        */
        #file{
            color: red;
        }
    </style>

</head>
<body>

<h2>标签</h2>
<p class="article">class</p>
<h3 id="file">id</h3>

</body>
</html>